The present invention relates to a device for a knock detection in an internal combustion engine.
More particularly, it relates to such a device, in which a knock sensor is linked via filter devices to an evaluation facility.
Devices for identifying knocking in internal combustion engines commonly have filters to which the output signals of a knock sensor are fed and which extract from these signals the frequency portions which are typical of knocking combustion. In a subsequent comparison arrangement, knocking is detected from these frequency portions when the signal portions which are typical of knocking are higher than the background signals ascertained from the entire signal spectrum or from the signal spectrum without portions typical of knocking.
A device or a method for detecting knocking and which embraces the named methods, is known from the DE-OS 33 42 466. To improve the reliability of knock detection, the output signal of the knock sensor of the known device or the known method is additionally amplified in an controllable amplifier, prior to filtering, so that the signal level remains approximately constant, independent of the number of revolutions. It is further proposed to configure the filter as a digital filter, with the facility that the transfer function of the digital filter can be selected dependent on the number of revolutions or on the load, by influencing the filter factor k.
However, the known device or the known method has the disadvantage that a frequency drift which may possibly occur is not taken into consideration, which makes a reliable knock detection more difficult.